Reduction of oxides



L. BURGESS REDUCTION OF OXIDES Filed Sept. 11 1920 WWW W A TTORNEY5 Patented Oct. at, 1924.

LOUIS BURGESS, or wnsrrrnnn, NEWJEBSEY, ASSIGNOR,

' 'ro Hmsnnr AND MAURICE BARNETT.

BY MESNE ASSIGNMENTS,

REDUCTION 0F OXIDEQQ Application fild September- 11, 1920. Serial No. 409,589.

To all wt am it may concemf k Be it known that I, LOUIS Bunenss, a c1t1-' zen of the United States, residing at Westfield, in the county of Union and State of New Jersey, have invented certain new and 'useful Improvements in the Reduction of Oxides, of whichthe following is a specification.

My invention relatesto new and useful improvements in the reduction of oxides and oxygenated ores of certain metals and metalloids, the vapor tensions of which, or.

the reduction produpts of which, are such that, volatilization losses occur at tempera- .tures practically necessary to effect reductionfor example, the oxides or ores of such metals as aluminum, zirconium and I beryllium, and of metalloids such as titabauxite (consisting nium, boron and silicon. In reducing these oxides in the presence of carbon in an electric furnace, appreciable los's'es occur, with consequenttlow yields of reduction products, because the oxide, or the reduced element, is volatilized and burned with the carbon monoxide evolved, and, therefore, cannot be recovered. L It is, therefore, the object of my present invention to efi'ecttheieduction of these oxides or ores in the presence of car-v bon, and in an electric furnace, without such volatilization as will result in material losses of the materials involved inthe reduction, or reduction products from such re action. With the end in .view stated, I 'perform the reduction. of the oxide in the presence of carbon and in an electric furnace,- and maintain the reactlon zone under such of the oxide or the reduction roducts is ma' teriallyreduced or prevents The invention is applicable to the reduc-' tion of pure, or substantially pure, oxides of said elements-for exam 1e, alumina or bauxite containing a high a umina content, silica or sand containing a high percentae of silica, boron trioxide, titania or ruti e, which is an ore containing a high percentage l of tltanlum ox1de,-beryll1a an zirconia; or

the ores or impure oxides thereof, such as rincipally of alumina and silica), borax, eryl (ore containing principally beryllia and silica) zirkite (ore containing principally zirconia and silica),

and clay (ore containing principally alumina and silica). The product resulting from the process is determined by the oxide or ore treated and the proportion of carbon employed, and may be briefly explained as follows: t, v

When using a pure, or substantially pure,

oxide-forexaniple, any of those above mentionedand suificient carbon, theproductwill be the substantially pure carbid.

'When using a pure, or substantially pure,

oxidefor example, .any of those above men-g .g,

the electrodes. Thus, in the first example 1. e., when using substantially pure oxides or orescarbon should be used in sufficient quantity to eliminate the oxygen present as CO-that is, in theoretical combinin portion-and sufiicient in excess of Sue portion to form a percentage 'of car id; while in the second example-i. e. when using the ores orimpure oxides.enough carbon shouldbe used to eliminate the oxygen propresent as CO, and, if necessary, to neutralme any tendency of the reduced materialto react With. the carbon structure of the furnace. J a

In the cases of the ores'f-it will be noted that certain of them consist of the oxide "of ametal (aluminum, beryllium-or zirconium), and a percentage of the oxide of a metalloid of the carbon group-e. g., silicon.

When reducing these ores according to m invention, it is only necessary to use enough carbon to ehmmate the oxygenas )()1. e., in theoretlcalcombimn proport1onsbecause the reduced metal oid neutralizes the tendency of the metal to absorb carbonactually used in the p shell 1, having {angles 6.

thereof, 1s, a bed 7 consisting 0 nace of this type,

scale of one-half inch 7 the furnace .rests,

result may be effected by making mixtures crude form of titanium oxide known as rutile, in place of silica, the product in such case being a titanid of the metal element, and an excess of the metal elementv or the metalloid element, accordinto which predominates chemically in t e mixture reduced. v

In carrying oat; the process constituting my present invention, I prefer to perform the reduction in an electric furna ce operating on the arc principle; and in the accompanying drawing and will describe the invention in connection therewith, although I. wish it understood that I do not limit my invention to the particular type of furnace shown, as I can perform the process many electric furnace which will efiiciently maintain proper conditions of pressure and temperature; I

In the accompanying drawings, Figure 1 is a View in vertical elevation, partly in vertical central section, of a preferred form of apparatus for practicing my invention.

c Fig. 2 is a section on the line 2-2 of Fig. 1. V,

Fig. 3 is a section on the line 3-3 of Fig. 1. 1 I

Fig. 4 is a detail vertical section through a stulfing-box employed.

Fig. 5 is a longitudinal section through a charging device, shown in elevation in Fig. 1. t .1

:Fig. 6 is a section at a right angle to that shown in Fig. 5, and

Fig. 7 is a detail sectional view trode-adjusting means employed.

In Figs. 1, 2 and 3 the drawings are ona to one (1) foot, f an apparatus I have erformance of the of elsebeing a reproduction 0 process.

Referring to ,the drawing, the furnace is of' a; cylindrical steel I p a c osed bottom or floor 2 and a head 3, the side wall or shell 1 extending above the head to provide a receptacle to retain a cooling fluid such as water I on the head to cool the latter. The sides and botto n'of the shell are lined with a suitable asbestos lining 4. The lower end of the shell 1 may also extend below the bottom: contents to the furnace.

port, as at 5, upon which and by which it may be. foundation, for exampl by the shell, and on'the b ttom f finely ground carbon, preferably. tamped into 2 to provide a sup secured to a I have illustrated a fur duit 21 and trough on this carbon bed isarranged a carbon element 8 constituting one electrode to provide the necessary-arc. ;'I'he" carbon element 8 is seated inawater-jacketed metal seat or holder 9, held in a socket or recess 10 in the wall 1 in the .side of the shell, by means of which electrical ;contact is established between said carbon element 8 and-the shell. The jacket 9 receives water "1 through an inlet pipe 11,=the water being discharged through an outlet pipe 12, the outlet of which'delivers the water upon the head of the apparatus. The water pools upon the head and may be drawn 0 through afpipe 13 containing a valve 14. Upon the carbon bed and oyer the electrode 8'is a pit 15,.the wall of which is built up of a plurality of carbon blocks 16, shown in section in Fig. 1, and in full and dotted lines in Fig. 3, said blocks b'e'ingspace apart from the shell 1 to provide an an 'nular space'l7, in which-space is tamped finely ground carbon 18, upon the .upper 'surface of which rests a fire-brick lining .19, which ,also rests upon the blocks 16.

place, and

In the side of the shell is a tap-hole 20 communicating with; an internal conduit '21, which communicates with a trough or groove 22 in the upper surface of the electrode 8. By means of thetap-hole 20, con- 22, molten reduced contents of the pit 15 may be withdrawn. The tap-hole 20 is closed by any suitable tight cap or closure 23 which will seal the taphole during running of the furnace, but which may be conveniently removed when the furnace contents are to be withdrawn. Above the furnace is a feed hopper or receptacle 24 adapted to contain the charge containing the oxide-to be reduced, and supported" by a suitable superstructure 25 on the furnace. This hopper 24 communicates with the interior of the furnace by means of feed pipes 26, the-discharge ends of which terminate within the chamber formed by the lining 19, and just abov e the pit 15. Each of the pipes 26 is provided with a feed mechanism 27, of any 'des'red type, prefermeasured charges of solid materials to the furnace. In Figs. 5 and 6 I have shown one of thesedevices in'detail, the same consisting of a casing 28 in the feed pipe, through .which casing extends a shaft 29 upon which are arranged vanes 30, preferably four in number, forming charge-receiving pocket 31, and also acting as valve means for establishing and cutting olf feed of the hopper The shaft 29 extends through stuffing-boxes 31, and carries on .one end a hand-operating device 32 by which the valve may be rotated to feed the charge at the desired rate.

1 Connected to and communicating with one of the pipes 26 is a pressure-relief pipe 4 26" carrying an automatic blow-off valve 26 is connected to a threaded sleeve 36 threadl tends through a stuuing-box 41 mounted on ed into the hub of a regulating wheel 37, said hub having a circumferential groove receiving bearing or retaining plates 39,,

supported by a cross-piece 39 on but insulated from brackets 40. mounted on the upper end of the furnace. The pipe 35 exa removable'head 42 closing amanhole 43 in the head 3 of the furnace. The stut'fing-box 41 comprises ashell 44 threaded, as at 45,

into the head 3, through which shell 44 exe tends the ine 35. Within the shell and surrounding the pipe, and forming a gastight joint between the pipe aid the shell, is an insulating packing, consisting preferably of rubber rings 46 surrounding the pipe 35 and held between blocks of asbestos-wood or other suitable material 47, the lower of which rests on a shoulder 47 on the sleeve 441 The rings are clamped between said blocks of asbestos-wood by means of a gland 48 resting on the upper block and pressed against the same by a packing nut 49 having a portion 50 threaded onto the shell 44 and having at its upper end an inwardly overhanging flange 51 which engages the upper end of the gland 48," By this arrangement,the pipe 35 may slide through i the stuffing-box, butescape of gas at this point from the interior of the furnace is prevented. Cooling fluid is admitted to the pipe 35 hy an internal pipe 52 fed through a hose 53 and coupling 54, and escapes through an outlet coupling 55 and 'hose 56,.

which also discharges onto the head of the furnace. The bearing 39 is properly insu lated from the supporting member 39. It will be seen that by rotatingthe Wheel 37, the electrode 33 may be vertically adjusted to vary the distance between the lowerend of the same, and the opposing electrode 8.

The electrical circuit is established by means ,of electrical connect ons 57, of any suitable type, electrically connected to the upper end of the pipe 35, and by a. bus 58 electrically connected, as at 59, to the shell 1, which, as heretofore stated, is electrically connected to the electrode 8. The furnace ispreferably provided with pressure gauges 60, and also with one or more exhaust valves 61,fby means of which the pressure may be regulated and the excessgas be permitted to escape, the valves 61 being located in pipes 61.

It will be understood that the furnace is' closed against escape of gases constituting the pressure medium, whether generated as the result of the reaction-for example, carbon monoxide-or established by admitting suitable gas to the furnacefor example, by: drogenor suitable hydrocarbon gas inert chemically to the materials involved. When gas is to be admitted from an external source, a suitable valved coupling .62 may be employed for the purpose.

In operating this furnace, a quantity of has been found that the maintenance of a voltage of about 42 volts and a current of about 1500camperes will result in a successful reduction, although I do not limit myself to the current conditions just mentioned, as different voltages and amperage may be employedfor example, as high as volts and 4000 amperesit being understood that the current condition is regu- .lated, in any suitable manner, so as to produce the desired temperature condition necessary to, perform the reduction. It will be -.understoodthat the regulation of the current conditions will vary with the size and construction of the furnace employed for the reduetionthatis, in small furnaces a low voltage and amperage'will operate successfully, while in larger furnaces greatr voltage and amperage may be employed in performing the operation. In the furnace illustrated I have employed successfully a voltage of 'and amperage of 4000. The feeding devices 27.are preferably operated so that the charge will be supplied at a uniform rate. I 1

When the current is established and the reduction takes "place, the gases generated, principally carbon monoxide, buildup in, a comparatively short time 'to a pressure of the desired degree, which I. prefer to be about 15 pounds to the square inch, in excess of atmospheric, and any excess pressure may be released, either manually or automatically, by a valve 61 in an exhaust maybe conducted for any period of time. in

practice found satisfactory, the pressure may be released and the reduction product, if molten, tapped out ofthe furnace through the duct 20. If the reduced material is not 55 form. of bauxite, which contains in its anmolten or fluid, it must, of course, be removed-by suitable mechanical means. Al though I prefer to employ a pressure of about 15 pounds to the square inch, above atmospheric, 1. may employ a pressure of, say, as high as 60 pounds to the square inch, and evenas high as 100 pounds.

The furnace above described will serve to.

efiiciently reduce the oxides of aluminum, zirconium, beryllium, titanium, boron and silicon, or combinations thereof, and I will now proceed to describe the constitution of the charge and the method of procedure fol lowed with the oxide material of each of these elements. The charge constituted, as hereinafter described, may be either a mixture of the finely divided oxide with carbon, so as ployed should be sufiicient to give a satisfactory; bond and produce the requisite amount of carbon material resulting from .the coking material, or free carbon'may be added so that the resultant coke charge contains thedesired percentage of carbon. The

result of 'this treatment is.to form a support-g ing structirre or matrix of coke through which the finely divided particles'of oxide are disseminated. Such a method is described in my co-pending application, Serial No. 317,687, filed August 15, 1919, now Patent No. 1,37 9,523, issuedMay 24th, 1921.

Aluminum om'de.-Wlfen it is desired to produce aluminum carbid employing relatively pure aluminum oxidei. e., alur '"mina-the charge is made up to contain the theoretical combining proportions of the oxide and carbonthat is, approximately 204 parts of the oxide to approximately 108 parts of carbon-the resulting product being aluminum carbid (A1 0 with a small --percentage of aluminum metal intermixed with the carbon, the aluminum carbid being substantially pure. By varying the proportions of the oxide and carbonfor example,

using 73 parts of the oxide-to 27 parts of carbon ,a mixture-of aluminum. carbid (A111,) and aluminum metal will be produced, in which the carbid does not exist in its pure state, but is mixed with the aluminum metal. This last formula ispreferred, as'it has the advantage that there:

duced material-pools well in the furnace and the carbon portions of the furnace structure are not attacked by the melt.

When employing aluminum oxide 1n the hydrous condition about 78% of alumina and about 19% of silica, I'use the theoretical amount of carbon necessary to reduce the aluminum and the silicon to elemental formthat is, approximately 76 parts by weight of bauxite to 24parts of carbonthe product being aluminum silicid (Ahfii and elemental aluminum.

I may also proceed by using 73 parts of bauxite to 27 parts of carbon, in which the product will be a. mixture of aluminum silicid (AhSielemental aluminum, aluminum carbid (A1 0,) and silicon carbid (SiC)., 7

This product has a higher melting point than that from the first-named foimula, and is easier to grind.

Titanium amide-In "reducing titanium oxide I use the crude form of the oxide known as rutile, which is mixe'd with the carbon in theoretical combining proportions of about 80 parts of rutile' t6 36 parts of carbon, the product being titanium carbid (TiC). By using a greater percentage of .rutile, thereby increasing the Eitaniumrarbid content in the reduced material, the product isa mixture of titanium and'titanium' carbid.

Zirconium oxide-In reducing zirconium oxide I preferably employ the crude form of the oxide, known as zirkite, and sufiicient carbon to eliminate the oxygen as carbon monoxide i. e., theoretical combining proportions, the 100 parts of zirkiteto 20 parts of carbon.

In this case the product is crude zirconium referred proportions being metal, which contains all the metallic and,"

metalloid products of-the zirkite in the form of an alloy or silicid. If desired, th e zirkite and carbon may be varied by increasing the amount of carbon, so that there will be sulficientto eliminate the oxygen as carbon monoxide, and a further quantity sufi'icient to form the carbon. The product zirconium carbid (Zr C' with minor percentages of silicon and si icon carbid.

Berylliumamz'de.-In reducing this oxide I employ the -'theoretical combining proportions of beryl (crude beryllium oxide) and carbon to eliminate oxygen as carbon monoxide, the 'proportions being by weight -100 parts of the beryl to 25 parts of carbon.

The product is beryllium silicid (Be Si with'a percentage of silicon. By 'increaslng' the. amount of carbon the product w11l contain beryllium silicid and a percentage of beryllium carbid (Be C B0 r0'n ow'ider-I this case, I employ the theoretical proportions of boron oxide (B 0 and carbon to eliminate oxygen as CO, and a further quantity of carbon sufficient to form a carbidfor example, 140 parts of boronoxide to 108 parts of carbon. In this case ,the product is substantially all boron carbid (B43 Silicon 0wide.-In this I employ the theoretical proportions of silica (SiO and carbon to eliminate oxygen as carbon monoxide, and a further quantity of carbon sutlicient to form a carbid with the siliconthat is, ,59 parts. of silica to 36 parts of carbon. The product in this case is silicon carbid (SiC). The percentage of silicon in the product may be increased by using less carbon.

In the cases of alumina, titania, boric oxide and silicon oxide, it is desirable to use the carbon according to the combining weights necessary to eliminate oxygen as carbon monoxide, andan additional quantity of carbon sufficient to form a substantial quantity of carbid, in order to prevent reaction between the oxide and any carbon structure of the furnace, so as to prevent destruction of the latter.

This is not necessary in the case of bauxite,

'clay, beryl and zirkite. because these materials reduce with theoretical'parts of carbon without attacking the carbon parts of the furnace.

The time of reduction, employing the furnace herein shown .anddescribed, and a current of voltage and amperage mentioned, would be in the neighborhood of one-half hour, working in a batch charge-that is. where the charge is not replenished as the reaction takes place. A

From the above, it will be seen that the product, when using substantially pure oxid'e with enough carbon. is the pure carbid y of the metal Br metalloid, but when using less than enough carbon to make the pure carbid, is a mixture of the carbid and the element. When using the oxide of the metallic elementsnamely, aluminum, zirconium and 'berylliilm instead of using an excess of carbon. I may use a theoretical proportion of carbon, elemental silicon or titanium mixed with the oxide, but in this cas the preferred method is to add the oxide of silicon or titanium and reduce it atthe samcoperation, iii which case the product is'a silici-d of the metallic element, or titanid of the metallicelement admixed with a percentage of either element employed. I

While I have described abovethe process embodying my invention as being performed in connection with certain named oxides, I

,1 desire it understood that a recital of these oxides is infno sense limiting, as the inventlon is applicable to-all oxides the vapor tensions of which, or the reduction products of which, are such that volatilization losses occur at temperatures practically necessary to effect reduction.

What I claim anddesire to secure by Letters Patent of the United States is:

The process of reducing metal and metalloid oxides,'which consists in subjecting divided oxide in contact with carbon to the direct heat of an electricarc in an enclosed space maintained under pressure of gas suilicient to prevent substantial volatilization. I

2. The process of reducing metal and metalloid oxides, which consists in subjecting the divided oxide in contact with carbon to the direct heat 01' an electric arc in an enclosed space mainta ned under pressure of gas generated by the reaction, and sufcharge during reduction.

4:. The process of reducing metal and metalloid oxides, which consists in subjecting a mass of divided oxide in contact with carbon to electric-heat in an enclosed space maintained under pressure of gas sufficient to maintain the boiling point of said mass above the temperature thereof.

5. The process of reducing metal and metalloid oxides, which consists in subjecting the divided oxide in contact with carbon to electricheat in an enclosed space maintained under pressure of gas generated by the reaction, said pressure being approximately -15 pounds to the square inch above atmospheric.

6. The process ofreducing metal and metalloid oxides, which consists in subjecting .a mass consisting of divided oxide-bearlicient to prevent substantial volatilization f o I n mg material encased in a supporting structure of coke to the heat of an electric arc. in an enclosed space maintained under pressure of gas generated by the reaction.

7. The process of reducing metal and inetalloid oxides, which consists in subject-- in; divided oxide in contact with carbon to the direct heat of an electric arc in an en-. closed space maintained under pressure of. gas chemically inert in relation to the materials involved. i

8. The process of reducing aluminum oxide, which consists in subjecting divided aluminum oxide in contactwith carbon to the direct heat of an electric arc in an enclosed space maintained under-pressure of gas chemically inert in relation to the materials involved.

9. The process of reducing aluminum oxide, which consists in subjecting divided aluminum oxide in contact with carbon to electric heat in an enclosed space maintained under pressure of gas at about 15 pounds to the squarei nch above atmospheric.

10. The process of reducing aluminum oxide, which consists in subjecting divided aluminum oxide in contact with carbon to electric heat in an enclosed space maintained under pressure of gas generated by the reoxide in contact with carbon to electric heat in an enclosed space maintained under pressure of gas, tapping the molten product, and replenishing the charge of divided oxide and carbon during reduction.

. In testimony Wh eof, I have hereunto signed my name, in the presence of two subscribing witnesses.

LOUIS BURGESS. Witnesses:

AGNEs E. CUNNEEN, D. L. WOOD. 

